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Federal drug agents have searched six Walgreens pharmacies and a company distribution center in Florida as part of an investigation into prescription painkiller drug abuse, U.S. Drug Enforcement Administration officials said Friday.

The distribution center in Jupiter and the six pharmacies — two in Fort Pierce and one each in Hudson, Port Richey, Fort Myers and Oviedo — all showed signs of suspiciously high distribution of the highly addictive drug oxycodone, a DEA investigator wrote in an affidavit for the search warrants.

The searches for pharmacy records conducted Wednesday are the latest in a crackdown by federal and state authorities on "pill mills" and other illegal sources of prescription drugs in Florida, which has become the nation's leading source of oxycodone and similar drugs. The DEA says that prescription drug abuse now exceeds abuse of all illegal drugs combined, except marijuana.

Michael Polzin, a spokesman for Deerfield, Ill.-based Walgreens, said it is cooperating in the investigation.

Earlier this year, the DEA moved to suspend the sale of similar controlled substances at two CVS pharmacies in the Orlando area, and the shipment of them from Cardinal Health Inc.'s Lakeland, Fla.-based center that supplied the stores. A federal appeals court recently upheld those suspensions.

DEA records cited in the Walgreens affidavit show sharp increases in oxycodone purchases at each of the locations. For example, the pharmacy in Fort Myers went from selling 95,800 units of oxycodone in 2009 to more than 2.1 million units in 2011 — good for 67 percent of all the oxycodone purchased by pharmacies in that same zip code in 2011.

In the first two months of this year, the DEA added, 53 Walgreens pharmacies are listed in the agency's top 100 purchasers of oxycodone. In 2009, none were on the list.

Earlier this year, the DEA released figures showing that Florida may be losing its distinction as the nation's leading illicit source for painkillers because of the ongoing law enforcement crackdown and several new laws. Florida also last year began operating a prescription drug tracking system and database aimed at combating illegal diversion of the drugs.

About 85 people, including at least 13 doctors, have been arrested in South Florida over the past year on pill mill-related charges, according to federal prosecutors.